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What is the trick to transmit a long way with low power that was not known 50 years ago?

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gary350

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I was reading online where it said, until we learned the trick to transmitting a long way on low power cell phones were not possible.

I remember 1969 electronic class project build a 100 mw transmitter, this thing would only transmit about 200 feet.

5 watt CB radio transmitted about 12 to 15 miles on a good day.

2 meter transmitter was the best but I don't recall distance or power.

Relative that works for NSA was telling me, bug transmitters store up voice in a zip file when the file is full it transmits on a carrier pulse 1/100 of a second it sounds like static to anyone listening.

What is the transmitter power of a cell phone?

WHAT is the trick to transmitting a long way on low power that was not known 50 years ago?
 

ronsimpson

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There are many things that happened in 50 years.
We now can transmit at higher frequencies, lower price, small size.
We now can receive at higher frequencies, lower price, small size, better signal to noise amps.
Higher frequencies makes high gain antennas small.
Better filters so noise rejections.
New ways of modulation. Remember AM, then FM, and SSB, etc.
 

crutschow

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Another factor is that many signals such as TV and cellphone are now sent in digital format with digital modulation of the RF signal so they can use error correction techniques of the data to compensate for signal errors that interference and noise might cause.
Thus you never hear or see noise in a digital audio or video signal.
You either receive a perfect signal or the signal drops out if it becomes too corrupt.
 

Nigel Goodwin

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I was reading online where it said, until we learned the trick to transmitting a long way on low power cell phones were not possible.
Perhaps you should read better websites? :D

Cell phones only transmit short distances, using fairly high power - that's the whole point of the 'cell' system.
 

gary350

Well-Known Member
Perhaps you should read better websites? :D

Cell phones only transmit short distances, using fairly high power - that's the whole point of the 'cell' system.
What is, Fairly high power? 100 watts? 500 watts?

What is short distance? 5 miles? 10 miles?
 

audioguru

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The earth is not flat anymore. If a distant signal does not bounce off the ionosphere then it is not received on earth, it goes out into space.
 

schmitt trigger

Well-Known Member
What both Ron and Crutschow mentioned.

We are now using both fairly advanced modulation schemes AND significant amounts of error correction and recovery techniques.

These techniques were known, at least conceptually, many decades ago. But to implement those, you would have required a pair of refrigerator-sized racks, drawing a pair of kilowatts of power.
Of course, with dedicated cooling units.

So if you ask me, what was the break-thru, I would say is a corollary of Moore's law: the ability to shrink that much computing power on devices which fit easily on a shirt pocket, while simultaneously running from a 3 volt battery.
 

MikeMl

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Using modern computationally-based error correction digital modes, Ham Radio folk are making the trip from earth to moon and back using ~50W and modest directional antennas. On the shortwave bands, using a new digital modulation/demodulation technique called FT-8, two-way trans Atlantic/Pacific contacts are happening every day at < 1W effective radiated power level.
 
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